This adopts a more guide-like writing style, similar to what prior commits
have done to some other subsections of this section.
The data sources page has not got any real attention since the feature
was first added, and our vocabulary for describing them and their
lifecycle hadn't quite settled when the page was originally written. This
new version is consistent in how it uses "data source" to describe the
feature that providers offer and "data resource" to describe what is
created by a "data" block in configuration, which then allows us to
draw on the many shared features between both data and managed resources.
For the moment this waits until "data resource" is defined in order to
first introduce the qualifier "managed resource". We may wish to revise
this again to mention that more specific nomenclature in passing on the
"Resources" page, in case a user encounters it elsewhere and wants to
learn what it means without needing to be familiar with data resources
first.
Martin Atkins